The present invention is related to switching devices. More particularly, the present invention provides a resistive switching device characterized by a controllable programming current with faster operation speed. Embodiments of the present invention have been applied to fabrication and operation of a resistive random access memory device. But it should be recognized that the present invention can have a much broader range of applicability.
The success of semiconductor devices has been mainly driven by an intensive transistor down-scaling process. However, as field effect transistors (FET) approach sizes less than 100 nm, problems such as short channel effect can degrade device performance. Moreover, such sub 100 nm device size can lead to sub-threshold slope non-scaling and also increases power dissipation. It is generally believed that transistor-based memories such as those commonly known as Flash may approach an end to scaling within a decade.
Other non-volatile random access memory devices such as ferroelectric RAM (Fe RAM), magneto-resistive RAM (MRAM), organic RAM (ORAM), and phase change RAM (PCRAM), among others, have been explored as next generation memory devices. These devices often require new materials and device structures to couple with silicon-based devices to form a memory cell, which lack one or more key attributes. For example, FeRAM and MRAM devices have fast switching characteristics and good programming endurance, but their fabrication is not CMOS compatible and size is usually large. Switching for a PCRAM device requires a high power. Organic RAM is incompatible with large volume silicon-based fabrication and device reliability is usually poor. Desirable attributes of a high density device should include high switching speed, reliable switching, and high endurance, among others.
From the above, a new semiconductor device structure and integration is desirable.